1. Technical Field
The present invention relates to a cooling and dust collecting apparatus of a machine tool for cooling a cutter and discharging cutting chips and particularly relates to a cooling and dust collecting apparatus of a centering machine for cooling a center drill and discharging cutting chips.
2. Related Art
There have been proposed various types of cooling and dust collecting apparatuses for machine tools. For example, Japanese Patent Laid-Open Publication No. Toku-Kai-Sho 58-59746 discloses a cooling and dust collecting apparatus for a machine tool in which a drill is surrounded by a hood and the drill is cooled by spraying mist of a cutting oil towards the center of the drill in several directions. Further, Japanese Patent Laid- Open Publication Nos. Toku-Kai-Sho 63-300807 and Toku-Kai-Hei 3-3713 disclose a pressure foot connected to a cutting chip suction device through a hose so as to keep the inside of the pressure foot in the negative pressure state and additionally, compressed air is blown from the vicinity of the front end of the pressure foot in the tangent direction of the drill. The compressed air expands in the pressure foot almost in an adiabatic state, thereby the temperature therein is sharply lowered. The compressed air thus cooled down cooled, cools down the drill of the drilling machine and is discharged to the cutting suction device together with cutting chips.
However, in the abovementioned cooling and dust collecting apparatuses for machine tools, since cutting oil mist or compressed air is blown to a cutter in a nearly horizontal direction, a portion of the cutter extending out of the workpiece is cooled, whereas the portion hidden therein is never cooled. In the type of the apparatus using a blowing oil mist, cutting chips tend to stick to the inside of the hood (pressure foot). Also, in the type of apparatus using blowing compressed air, sufficient air flow for discharging cutting chips can not be obtained in the hood. Consequently, in these types of cooling and dust collecting apparatus, it is difficult to adequately discharge cutting chips, especially when the workpiece is metal having a large specific gravity.
It is known that the heat sources of heating of the cutting tool are the heat generated by cutting and the heat transferred from the cutter driving section. In the prior cooling and dust collecting apparatus, no attention has been paid to the heat transferred from the cutter driving section, and therefore sufficient cooling of the cutting tool has not been achieved.